In the related art, a semiconductor thin film of polycrystalline silicon (poly-Si) or the like is widely used for a thin film transistor (TFT) or a solar cell. As a method of forming the film at a low cost, an amorphous silicon film is irradiated with a laser beam to be crystallized. A laser process can be also applied to activation of impurity atoms introduced to a semiconductor substrate by ion implantation or plasma doping. However, in the laser annealing technology, problems arise in that an end-point temperature varies depending on the magnitude of light absorption of a heating-target object or a joint line appears, or significantly high-cost equipment is required.
Therefore, technology, in which elongated thermal plasma is generated and scanning is performed only in one direction, thereby making it possible to perform heating without dependence on the light absorption of the heating-target object, or thermal processing is performed at a few cost without the joint line, has been studied (for example, see Japanese Patent Unexamined Publication No. 2013-120633, Japanese Patent Unexamined Publication No. 2013-120684, Japanese Patent Unexamined Publication No. 2013-120685, and Jpn. J. Appl. Phys. 52 (2013) 05EE01, by T. Okumura and H. Kawaura).
However, a common problem in the plasma processing is so-called electrostatic damage. The electrostatic damage is a problem in that an equilibrium state of an electron current and an ion current flowing to the heating-target object (substrate) is locally disturbed due to spatial heterogeneity of plasma and electric charge is accumulated. As a result, in a case where the substrate contains a transistor, problems arise in that a gate insulating film is degraded due to tunnel current and a dielectric strength voltage becomes lower or a voltage of a flat band voltage is changed (for example, see “Development of plasma charge-up damage evaluation wafers” in Kobe Steel Engineering Reports, Vol. 52 (2002) p. 83 by Yoshito Fukumoto and Shingo Sumie).
In capacitively coupled low-temperature atmospheric pressure plasma used in surface cleaning or the like, there is a method called a remote type in which it is possible to suppress an increase in the electrostatic damage. When a direct type, in which the substrate is disposed inside a plasma space, is compared to the remote type, in which the substrate is disposed outside the plasma space, the remote type is considered as posing a smaller risk of electrostatic damage (for example, see Japanese Patent Unexamined Publication No. 2003-100646).